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Tire Pressure Monitoring Systems: How They’ll Work and What They Mean to You


Maintaining the proper inflation in tires is a subject that is as old as tires themselves. This issue has been likened to keeping the right amount of oil in the car’s crankcase – don’t do it and the engine will fail.


The good news is that air doesn’t need to be changed periodically – though some people have probably even tried to sell that idea.

While air doesn’t wear out or become contaminated in normal use, high-pressure inflation is required to allow the modern tire to fulfill its multi-task function.

There’s no question that today’s tires perform much better than their predecessors. Tire manufacturers continue to take advantage of new materials, processes, and computer-based design and testing tools. Every significant tire performance vector has improved, and advances have been made from the days when any performance gain was often at the expense of some other attribute.


The same can be said for most highway vehicles available today. Cars, light trucks and commercial trucks perform reliably, provide significant comfort, convenience and safety, and are available in a near endless variety of sizes and configurations. The list of possible options is longer than ever.

The combination of choices and the impressive overall record of trouble-free tire performance may have conspired to lull many vehicle owners into a potentially dangerous sense of security.

Perhaps we believe that little or no maintenance is required for the vehicles – and tires ®€“ that do most anything we ask of them.

TREAD Act-ion

Last year’s tire recall prompted Congress to enact the Transportation Recall Enhancement Accountability and Documentation Act – the TREAD Act. The new law directs NHTSA to address a number of issues, including revisions to FMVSS109 and 119 vehicle and tire standards, and the performance and labeling standards for highway tires, tire claim reporting and an "early warning system", and some type of in-vehicle warning system to alert drivers of underinflated tires.


This year’s Ford tire recall will create even more regulation. But that’s another story yet to unfold.

The TREAD Act’s tire pressure monitoring system requirement, however, is the basis for a great deal of speculation and a sharp rise in activity among tire companies, vehicle makers and independent firms working on their own pressure warning systems.

NHTSA is on a tight schedule to publish a final ruling by early November of this year (with an effective date of November 2003 for fitment on new vehicles). The ruling will detail the requirements for tire inflation pressure monitors that will warn drivers of any "substantially underinflated" tire.


While the original mandate addresses all highway tires, some believe that only tires covered by FMVSS109 will be included in this first rulemaking. Larger commercial truck and trailer tires covered by FMVSS119 would be addressed later. While this is a very logical approach, there’s no telling which direction NHTSA will go.

Numerous companies are working on devices to meet expected government rulings. There will be as many systems as there are types of vehicles. And, no doubt, the differences and similarities will be driven by the obvious variety of vehicle sizes, and the tire/wheel complexities ranging from simple four wheelers to 42-wheeled Michigan train truck-trailer units.


Three Separate Issues

Tire Review recently reviewed the efforts of companies developing pressure monitoring systems and have tried to categorize the approaches based on intended application and technology.

There are at least three significantly different application situations, namely consumer or personal use vehicles, commercial trucks, and heavy OTR vehicles.

Consumer tires have been the primary focus of the TREAD Act mandate. Some believe this market can be best addressed with a simple dashboard display, like a red light that alerts the driver to a tire problem – similar to an oil warning light.

This is a "passive" system, informing the driver to stop and take steps to correct his/her tire inflation level. Finding a means to reinflate the problem tire, using caution while driving to reach that source, or seeking a way to change a flat tire are all decisions that such a passive system would leave to the driver.


Presumably, the vehicle manufacturer, working in concert with tire engineers and using established industry guidelines, would be responsible for setting the low pressure threshold that triggers such a driver warning.

However, such variables as hot vs. cold pressures, changes in ambient conditions, and sensor variations may cause these "stacked" tolerances to become large enough that target inflations must be raised.

These passive systems, however, would not address overinflation, inflation balance, vehicle overloading, and other variables that impact tire life or vehicle handling/stability.

Some companies are working closely with automakers to develop "active" systems that will maintain the correct inflation pressure for particular vehicle/tire combinations. These active systems vary in complexity, sophistication, and cost.


Some top-line systems include run-flat tires, on-board make-up air, and "smart" software that would compare four corners to distinguish between a tire that is running marginally low, has a slow leak, is ill-maintained, or has a more urgent puncture or damage condition.

Building Alliances

Seeing the TREAD Act writing clearly on the wall, many tire makers have already struck cooperative or joint venture deals with high-tech electronics firms and/or companies developing tire pressure monitoring systems.

Goodyear has paired with both Cycloid Co. and Phase IV Engineering in separate efforts to develop an OE system, and has also test-marketed retail sales of a Johnson Controls-created system in the Detroit area.


Continental AG and Siemens co-developed a tire performance monitoring system as part of Continental’s continuing "intelligent tire system" program.

Canada’s SmarTire Systems gained exclusive rights from TRW to make and sell a monitoring system to both the OE and replacement trucking market. Just last month Groupe Michelin licensed an acoustic wave technology from Transense Technologies plc, for an undescribed pressure warning device it is developing. SmarTire also has license to use Transense’s technology.

In Europe, Nokian Tyres is combining a high-tech in-wheel monitoring system with the common cellular telephone. While the Finnish company has delayed the rollout of its RoadSnoop Safety System, co-developed with Flextronics International, the system will warn drivers directly through their Nokian phones.


And surely Yokohama, Toyo, Cooper and others are working to develop their own system concepts.

Vehicle Makers’ Role

A common thread among those working on consumer vehicle monitoring systems is that all of them stress the vital role of the vehicle manufacturer. Car engineers are familiar with the unique relationship between tire performance and inflation pressures and the handling/stability of their individual chassis/platform designs.

Most of the pressure-sensing device concepts being promoted include electronics and radio frequency communications, making electronic signal compatibility a high priority and requiring a joint development effort. In other words, system standardization could be vital.


Other companies, like SmarTire, have developed systems that use sophisticated sensors mounted on each wheel to collect tire chamber pressure and temperature data, which is then transmitted to a receiver/display mounted in the vehicle. Although this modular system is designed for universal fitment, including the aftermarket, it’s planned for OE use on new high-end OE vehicles.

Commercial Applications

The second group of systems being developed applies to the commercial vehicle market, including straight trucks and tractor-trailer combinations. Most of these vehicles are company-owned and driven by hired drivers.

Since medium and heavy truck tires are the second largest expense item in most fleets (fuel ranks first), fleet operators are keenly aware of the need for diligent tire maintenance. Tire casings are treated as bottom line assets, and underinflation that ruins a casing for future retreading is a financial negative.


Most truck operations have in-house maintenance facilities for routine service, including tires, or contract with outside parties specializing in vehicle and/or tire maintenance. Through experience, most of these operators have strong opinions about what tire inflation levels are optimum for their trucks and service conditions, and have systems in place to maintain their tires.

While fleets generally don’t want drivers setting or adjusting tire inflations, drivers are expected to periodically inspect and report tires for cuts, bulges, other damage, and unusual wear conditions of concern.

Also, the typical large fleet may have many more trailers than power units, and the trailers are often parked at customer loading docks or storage yards, making maintenance more difficult and less reliable. This also adds to the maintenance dilemma.


Several companies have tackled these trailers with automatic inflation systems that use dry high-pressure air stored in the trailer brake reservoir. These systems maintain all trailer tires at a preset inflation level. Air is routed to a control box that regulates pressure, then into each trailer axle tube to a rotary union assembly at the spindle end, and, finally, to each tire as needed. These systems won’t deplete the brake air supply and have check valves to prevent air loss from other tires in the event that one tire fails.

Thousands of these systems are currently operating successfully in North America. Users like Union Pacific report huge tire expense reductions. Use of these systems in intermodal and container chassis fleets may hasten the conversion of this last group of bias-ply truck tire users to radials.


ArvinMeritor currently offers its PSI tire inflation system, developed by Pressure Systems International, through most OE trailer manufacturers. Innovative Transportation Products (ITP) has a similar system called PressureGuard. Retail pricing for these systems adds approximately $600 to $750 to the price of a new trailer.

It’s important to distinguish these "active" systems from "passive" pressure equalization systems, which are designed to improve tire wear, durability, and fuel economy by assuring that tire pressures are equalized in sets of duals.

However, this innovative approach becomes more difficult when applied to steer and drive axles, since these don’t typically have the hollow spindles for air routing. And sealing, lubrication, and other design issues are more complex.


Arguably, the need for inflation monitoring on power units is much diminished compared to trailers, due to the higher frequency and depth of routine maintenance. Several manufacturers, however, say they plan to have systems for drive axles in production in the next 12-24 months.

Other manufacturers also currently have systems available for the truck market. For example, Dana offers a system based on its experience in military and logging truck applications. These systems are relatively complex and use air from an independent source.

Heavy Weight Systems

A third group of devices address needs of earthmovers, loaders, scrapers, and other heavy equipment. These systems are more complex, more expensive, and designed to operate in a wide variety of hostile service environments. They are better characterized as "tire program management systems" rather than inflation monitoring devices.


Temperature monitoring is desired, since tire performance is considered in terms of ton-miles-per-hour, and is limited by the combination of load and speed they’re designed to endure. Temperature history is also important as this can be related to a casing’s durability and the tire’s projected length of service.

OTR tire makers agree that pressure monitoring should be combined with temperature monitoring, and the system should record operating history, at least in terms of peak temperatures or time/temperature history, and perhaps cumulative revolutions.

Acquisition and transfer of this information is handled by an electronic chip placed inside the tire and an accompanying receiver/reader unit – either in-cab or at the work site. These systems are labeled "active" if the chip is battery powered and "passive" if the collected data is "beamed up" using RF transmitter technology sourced at the receiver.


Several tire makers are working with component suppliers to refine these systems. Since many of these tires are leased or sold on the basis of performance delivered, tire makers have an incentive to assure optimum maintenance tailored to operating conditions and to guard against customer abuse.

What About Dealers?

Nearly all of the companies we contacted said the next six months will be critical in determining the final architecture of this complex issue. There’s no question that proper tire inflation specification and driver warnings for consumer vehicle applications are front burner issues.

One question that needs an answer is: Will there be a single standard for inflation monitoring systems? If there are as many systems as there are players, tire dealers will be faced with a multitude of training issues. It will take NHTSA – or an agreement between numerous parties ®€“ to address this important aspect.


Unclear are a number of other important questions for tire dealers, especially retail dealers. Will these systems change the way you demount and mount tires? How will they interrelate with other vehicle systems? Are there ways to leverage these systems to improve customer relationships? Do opportunities for dealers to sell/install aftermarket systems on pre-2003 vehicles? Will better consumer attention to tires (thanks to these systems) change businesses? Will OE systems limit consumer selection of replacement tires – by brand, size or load rating?

There will be lots of discussion within the industry in coming months. The degree of standardization or diversity of offerings will be influenced by these ongoing discussions. For now, all we can do is watch and wait.

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